There have been air-conditioning and hot water supply combination systems, each of which is equipped with a refrigerant circuit including a heat source unit (outdoor unit), a use unit (indoor unit), and a hot water supply unit (water heater) such that the use unit and the hot water supply unit are connected to the heat source unit through pipes, and is capable of simultaneously executing an air-conditioning operation and a hot water supply operation (refer to Patent Literatures 1 to 3, for example).
In such an air-conditioning and hot water supply combination system, a plurality of use units are connected to the heat source unit through connecting pipes (refrigerant pipes), so that each use unit can execute a cooling operation or heating operation. In addition, the hot water supply unit is connected to the heat source side unit by connecting pipes or a cascade system, so that the hot water supply unit can execute the hot water supply operation. In other words, the air-conditioning operation by the use side unit and the hot water supply operation by the hot water supply unit can be simultaneously executed. Furthermore, in the case where the use unit performs the cooling operation in the air-conditioning and hot water supply combination system, execution of the hot water supply operation by the hot water supply unit enables to recover exhaust heat in the cooling operation, thus achieving highly efficient operations.